[[TFM]] has written ROMManager which can create these accessory ROMs and he provides downloads on his website for some that he has made himself.
[[User:Cormacj|CormacJ]] has written a python script to create accessory ROMS and also extract .COM files from ROMS. You can view this at his [https://github.com/cormacj/AmstradCPCRomHacks?tab=readme-ov-file#make_accessory_rompy AmstradCPCRomHacks] repository
Some emulators don't support the accessory ROMs because of the non-standard format. Arnold and Caprice32 supports these.